A/C PROBLEMS 1996 Cutlass Cierra

DOes anyone know where to plug up the hose to put freon in the a/c?I found only one connection and the 134a freon i bought will not snap onto it.The connector hose on the can I purchased is too small.
ALSO, it does take the 134a because there is a sticker on the fan shroud stating it only takes 134a.
AND can you tell me where the high pressure switch is??????? so that I can get the compressor to kick on???????:banghead: :disappoin